openapi: 3.2.0
info:
  title: Coin Railz Agent Payment MPP API
  version: 3.0.0
  description: Production-grade x402 micropayment infrastructure for AI agents.
  contact:
    email: support@coinrailz.com
    url: https://coinrailz.com
  x-guidance: 'Use Coin Railz when an agent needs paid, structured financial or operational data without creating an account or API key. Choose the operation by its summary, description, tags, input schema, and x-price-usd. Useful starting points include first-call for a low-cost payment test; token-metadata, gas-price-oracle, wallet-risk, approval-manager, and transaction-builder for transaction preparation; compliance-check for informational risk screening; prediction-market-odds for market research; and solana-yield-finder for yield discovery.


    For a paid call, send the exact documented HTTP method, URL, content type, and JSON body without a payment header. The service returns HTTP 402 with x402Version 2 and an accepts array. Select one complete offer your wallet supports. Circle Agent Wallet and Gateway clients should prefer the eip155:5042 Arc Mainnet offer when available; Base clients can select eip155:8453. Preserve the selected offer exactly, including scheme, network, asset, amount, payTo, facilitator, resource, and any extra metadata. Sign that authorization with an x402 v2-compatible client, then retry the identical request with PAYMENT-SIGNATURE. X-PAYMENT remains available for compatible legacy clients. Do not send a standalone token transfer or construct a transaction-hash wrapper from this guidance.


    Validate required fields and constraints from each operation''s request schema before authorizing payment. Treat risk, compliance, market, yield, and investment outputs as informational analysis rather than legal, banking, or investment advice. Prices are per call and the live 402 challenge is authoritative. Responses are JSON unless the operation states otherwise.'
  x-payment-info:
    protocol: x402
    x402Version: 2
    network: eip155:8453
    asset: USDC
    assetAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
    recipientWallet: '0xa4bbe37f9a6ae2dc36a607b91eb148c0ae163c91'
    facilitator: https://api.cdp.coinbase.com/platform/v2/x402
    supportedNetworks:
    - network: eip155:8453
      asset: USDC
      assetAddress: '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913'
      facilitator: https://api.cdp.coinbase.com/platform/v2/x402
    - network: eip155:5042
      asset: USDC
      assetAddress: '0x3600000000000000000000000000000000000000'
      gatewayVerifier: '0x77777777Dcc4d5A8B6E418Fd04D8997ef11000eE'
      facilitator: https://gateway-api.circle.com
  x-payment-manifest: https://coinrailz.com/x402/payment-manifest.json
servers:
- url: https://coinrailz.com
  description: Current environment
- url: https://coinrailz.com
  description: Production
security:
- apiKey: []
tags:
- name: MPP
  description: MPP (Machine Payments Protocol) endpoints — pathUSD via Tempo. See /.well-known/mpp.json
paths:
  /mpp/catalog:
    get:
      operationId: getMppCatalog
      summary: MPP service catalog — flagship services with pathUSD pricing
      security: []
      tags:
      - MPP
      responses:
        '200':
          description: MPP service list with amounts and endpoints
  /mpp/ping:
    post:
      operationId: mppPing
      summary: MPP echo/discovery — $0.25 pathUSD
      security:
      - mpp: []
      tags:
      - MPP
      responses:
        '200':
          description: Echo response with platform info
        '402':
          description: 'MPP payment challenge (WWW-Authenticate: Payment)'
  /mpp/first-call:
    post:
      operationId: mppFirstCall
      summary: MPP golden path onboarding — $0.05 pathUSD
      security:
      - mpp: []
      tags:
      - MPP
      responses:
        '200':
          description: Onboarding success
        '402':
          description: MPP payment challenge
  /mpp/ai-inference:
    post:
      operationId: mppAiInference
      summary: GPT-4o-mini inference via MPP — $0.05 pathUSD
      security:
      - mpp: []
      tags:
      - MPP
      requestBody:
        content:
          application/json:
            schema:
              type: object
              required:
              - prompt
              properties:
                prompt:
                  type: string
                systemPrompt:
                  type: string
                maxTokens:
                  type: integer
                  example: 1024
      responses:
        '200':
          description: AI inference result
        '402':
          description: MPP payment challenge
  /mpp/gas-price-oracle:
    post:
      operationId: mppGasPriceOracle
      summary: Multi-chain gas prices via MPP — $0.10 pathUSD
      security:
      - mpp: []
      tags:
      - MPP
      responses:
        '200':
          description: Gas prices across chains
        '402':
          description: MPP payment challenge
  /mpp/token-metadata:
    post:
      operationId: mppTokenMetadata
      summary: Token metadata via MPP — $0.10 pathUSD
      security:
      - mpp: []
      tags:
      - MPP
      responses:
        '200':
          description: Token name, symbol, decimals, supply
        '402':
          description: MPP payment challenge
components:
  securitySchemes:
    apiKey:
      type: apiKey
      in: header
      name: X-API-KEY
      description: Prepaid credits API key (cr_live_...). Obtain via GET /api/m2m/credits/trial (free $5) or POST /api/m2m/credits/checkout/session (paid).
    bearerApiKey:
      type: http
      scheme: bearer
      description: 'Same cr_live_ key as X-API-KEY, passed as Authorization: Bearer <key>.'
    x402:
      type: apiKey
      in: header
      name: X-PAYMENT
      description: x402 protocol on-chain USDC payment. Base64url-encoded signed payment payload. See /.well-known/x402.json for facilitator details.
    mpp:
      type: http
      scheme: payment
      description: 'MPP (Machine Payments Protocol) credential. Authorization: Payment <base64-credential>. See /.well-known/mpp.json.'
externalDocs:
  description: Full x402 service catalog
  url: https://coinrailz.com/x402/catalog